DEAR JOAN: There is a wire across Highway 85 -- between Saratoga Avenue and Los Gatos -- that is always full of birds whenever I drive by. I am wondering why this particular wire, when others are empty.

Kathy D.

Bay Area

DEAR KATHY: To know for certain, I think we'd have to ask the birds. My guess is that it's in a place that suits the birds' needs.

Birds like have a good vantage point to keep an eye out for food opportunities and for oncoming trouble. That's why you see them perched on wires in the first place.

But let's say you walk in the park every day, and every day you stop for a few minutes and sit on a bench. Perhaps another walker will join you there, too, and you spend a few minutes in friendly conversation.

You chose that bench for a number of reasons. You were tired, it's a sunny spot, it's a good place to people watch. Whatever the reason, you picked it and now come back to it for those reasons and because it has become a habit.

That's likely what's going on with the birds. It might also have something to do with voltage and electromagnetic fields, but I prefer the other explanation.

Benefits of mud

In late December, a sea lion was found swimming up Cerrito Creek toward Richmond's Pacific East Mall, at the foot of Albany Hill. The Marine Mammal Center rushed to rescue the sea lion, which now is recovering at the center.

The sea lion was suffering from domoic acid, a deadly toxin that is produced during a harmful algal bloom known as a red tide. The concentration of the algae can give the water the appearance of having a smear of red on the surface of the water, although not all concentrations are red or even visible.

Shellfish eat the algae, then sea creatures, including sea lions, eat the shellfish, making them ill.

Researchers say the algal blooms are becoming more common in San Francisco Bay, and the reason is sort of surprising: The bay isn't dirty enough to prevent them.

According to a news release from Friends of Five Creeks, the water in the bay is becoming clearer, and that's not necessarily good news. If the water was more muddy, that would block some of the sunlight that stimulates algae growth.

Efforts to keep the water cleaner, such as dams that trap the sediment from mountain erosion and the general hardening of shorelines, keeps the water clearer. The mud that washed into the bay a century ago during hydraulic mining has not been replenished, and the lack of significant rain means there is even less erosion from water runoff.

That doesn't mean we should all go dump mud in the bay, but we often talk about the balance of nature and what a tricky job it is. This shows us that it may be more difficult than we thought.

If you're interested in learning more about this, Friends of Five Creeks will host a talk, "Mud Matters," at 7 p.m. Feb. 3 in the Edith Stone Room, Albany Community Center, 1249 Marin Ave. (at Masonic). Jeremy Lowe, senior coastal geomorphologist, will talk about the historic and current role of mud in the bay, what controls its availability and how, in the face of sea-level rise, undervalued resources such as mud and wastewater can be critical in creating new, more sustainable shorelines.

Contact Joan Morris at jmorris@bayareanewsgroup.com or 1700 Cavallo Road, Antioch, CA 94509. Follow her at Twitter.com/AskJoanMorris.